1. Field of the Invention
The present invention relates to a fusing device in an image forming apparatus, such as a laser beam printer, a multi-function machine, a photocopier, or the like, and more particularly, to an apparatus for and a method of regenerating an outer coating layer of a fusing roller of a fusing device in an image forming apparatus when the outer coating layer is contaminated, damaged, or worn out.
2. Description of the Related Art
A general image forming apparatus using an electrophotographic developing method, such as a photocopier, a laser beam printer or the like, prints a desired image on a sheet of paper by the following processes, i.e., by electric charging, light exposure, developing, transferring, and fusing operations. The electric charging operation is to electrically charge a surface of a photosensitive drum by rotating an electrostatic charging roller disposed adjacent to the photosensitive drum. The light exposure operation is to scan the surface of the photosensitive drum with a laser beam projected from a laser scanning unit (LSU) to thus form an electrostatic latent image on the surface of the photosensitive drum. The developing operation is to develop the electrostatic latent image formed on the surface of the photosensitive drum to a toner image of a powdery state, i.e., a visible image, by supplying toner to the surface of the photosensitive drum. The transferring operation is to transfer the toner image formed on the photosensitive drum to a recording medium i.e., to the paper passing between the photosensitive drum and a transferring roller being in contact with the photosensitive drum with a predetermined pressure, while a predetermined transferring voltage is supplied to the transferring roller and the photosensitive drum. In the fusing operation, a fusing device including a fusing roller heats the paper with the toner image being transferred thereon, fuses the toner image of the powdery state to a liquid state, and settles down the toner image onto the paper.
Generally employed as a heating source of the fusing device is a halogen lamp. The halogen lamp is disposed inside the fusing roller and a fusing backup roller to heat surfaces of the fusing roller and the fusing backup roller to a predetermined temperature with a radiant heat, thereby fusing the toner image onto the paper.
FIG. 1 schematically shows an example of a fusing device 10 of a general electrophotographing image forming apparatus.
The fusing device 10 includes a fusing roller 1 that has a first metal core 4 shaped in a cylinder and a first heater 3a. A surface of the first metal core 4 is coated with a silicone rubber having an anti-adhesiveness to form a silicone coating layer 5. The first heater 3a is disposed in a center of the first metal core 4 and uses a halogen lamp, thereby generating radiant heat inside the first metal core 4. Accordingly, the first metal core 4 is heated by the radiant heat from the first heater 3a. 
Under the fusing roller 1 is disposed a fusing backup roller 2 that includes a second metal core 15 shaped in a cylinder, and a second heater 3b disposed in a center of the second metal core 15 and using a halogen lamp. The fusing backup roller 2 is resiliently supported by a spring (not shown) so that it presses a sheet of printing paper 11 passing between the fusing roller 1 and the fusing backup roller 2 toward the fusing roller 1 with a predetermined pressure.
Also, under the fusing backup roller 2 is disposed an agent supplier 8 formed of Teflon to supply an agent 7 having a function of releasing the printing paper 1. Also, a blade 9 is disposed under the fusing backup roller 2 to evenly supply the agent 7 to the fusing backup roller 2.
Accordingly, while the printing paper 11 passes between the fusing roller 1 and the fusing backup roller 2, the toner image 14 formed on the printing paper 1 in a powdery state is subjected to a predetermined pressure and a predetermined heat. Due to the pressure and the heat applied on the fusing roller 1 and the fusing backup roller 2, the toner image 14 is fused onto the printing paper 11 at a nip 12 formed between the fusing roller 1 and the fusing backup roller 2.
Each of the fusing roller 1 and the fusing backup roller 2 is provided with a thermistor 6 and a thermostat (not shown) respectively disposed at a side thereof. The thermistor 6 is for detecting surface temperatures of the fusing roller 1 and the fusing backup roller 2 in an electrical signal form, and the thermostat blocks a power from being supplied to a heating unit, such as the first or second heater 3a, 4b, when the surface temperatures of the fusing roller 1 and the fusing backup roller 2 exceed a given threshold.
The thermistor 6 detects the surface temperatures of the fusing roller 1 and the fusing backup roller 2 and transmits the detected result (temperature) to a controller of the image forming apparatus. The controller regulates a power supply to the first and the second heaters 3a and 3b according to the detected temperature, thereby maintaining the surface temperatures of the fusing roller 1 and the fusing backup roller 2 within a given range.
The thermostat also functions as an overheat preventing unit to protect the fusing roller, the fusing backup roller 2 and their neighboring components in a case that the thermistor 6 and the controller fail to regulate the surface temperature of the fusing roller 1 and the fusing backup roller 2.
However, in the conventional fusing device 10 as described above, since the toner image 14 is fused onto the printing paper 11 due to the heat and the pressure applied on the fusing roller 1 and the fusing backup roller 2, if the fusing operation repeats for a long time, the coating layer 5 of the fusing roller 1 fusing the toner image onto the printing paper 11 is contaminated with the toner image 14 and thus an image quality deteriorates.
In order to prevent the image quality deterioration caused by the contamination of the coating layer 5, conventional methods have been suggested. One method is for coating the coating layer 5 of the fusing roller 1 with anti-adhesive oil to improve an anti-adhesiveness of the coating layer 5 and simultaneously projecting visible light or infrared light onto the coating layer 5 to dissolve a contaminated material into a low molecular oxide, such as dioxide carbon, water, or the like, and thus remove the contaminated material. The other method suggests a cleaning device of the fusing roller 1 to clean the fusing roller 1 in a standby mode for a predetermined time and coat the coating layer of the fusing roller with the anti-adhesive oil, thereby preventing the image quality deterioration. The former method is disclosed in Japanese Publication No. H12-347526, and the latter one is disclosed in Japanese Publication No. H13-125417.
The above cleaning devices may remove contaminants from the fusing roller 1 by cleaning the coating layer 5 of the fusing roller 1, but the cleaning devices cannot remove the contaminants when the coating layer 5 deteriorates, and thus the fusing roller 1 is damaged due to a long time use. In this case, it is inevitable that the fusing device 1 has to be entirely replaced with a new one to maintain the image quality.
As described above, since a life span of the conventional fusing device depends on the coating layer of the fusing roller, when the coating layer is damaged, the fusing device has to be replaced with a new one even when components other than the coating layer operate in a normal condition. Accordingly, there occur problems of waste of resources and increased maintenance costs.